I Spy With My Little Eye...

The calorific value of the fuel is less significant than the way it combusts. The best combustion conditions are a balance between ignition advance, jetting and compression ratio. When you change fuel that balance needs to be re-adjusted to maintain performance levels. Jetting adjustments are used to compensate for different latent heats of vaporisation. A higher latent heat of vaporisation causes the carburetor to be colder and the air in the inlet tract to be denser, so a bigger jet is needed, to maintain the balance.
I use methanol fuel at 9 to 1 compression ratio with 33 degrees of ignition advance, and with a 0.117 needle jet. If I raised the compression ratio to 12 to 1 compression ratio to 12 to 1, I would probably use 29 degrees ignition advance and a 0.120 needle jet. My bike would probably not be any faster.
A lot of guys believe bullshit - their biggest mistake is usually increasing the inlet port diameter. A lot of guys do not understand the relationship between jetting, gearing and the way the bike handles. When you are developing the bike, you need to learn how to use it effectively. A rocket ship down the straights is usually slower in corners. I would much rather crash in a corner than when braking at the end of a straight.
 
Getting back to cylinder walls-
every engine that I ve taken apart has a few vertical lines on the cylinder wall. Most cannot be felt. If you can feel them with a fingernail, then that is a problem.

Glen
 
My mate's 650cc Triton is probably a better way to go than my Seeley 850. It is fast in a straight line and is neutral handling - easier to ride fast. The Seeley is very different. It took me a while to learn how to use it.
 
worntorn said:
Getting back to cylinder walls-
every engine that I ve taken apart has a few vertical lines on the cylinder wall. Most cannot be felt. If you can feel them with a fingernail, then that is a problem.

Glen
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The necessity of checking the seating of the circlips in the pistons is probably not obvious to many people.
 
worntorn said:
probably not as it could cause serious problems in a very high compression engine.
As Nortonbob pointed out- my hill testing only shows what works best in my bike.
I should remember that and perhaps not try to share info that might or might not work for others.

Glen
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I'm sure somebody gets something out of the personal tests anyone does. By the way, I've thought the same about my P11 modification posts many times, but I'll still kept doing it.
 
Thinking some more on this, the exhaust testing should be relevant to anyone with a stock 850.
The fuel testing results were virtually the same with my Vincent 998 as with the Commando, so that will apply to a great many engines, basically anything that will run on reg without pinking.
The electrical/charging testing I did would be applicable to anyone using a Podtronics reg/rec.
These were all repeatable values, not seat of the pants.
On performance testing I always make a seat of pants analysis before doing the hill testing. My seat of pants is almost always wrong!
So I think the hill and other testing info should be useful to others.


But you can only lead a horse to water..
 
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worntorn said:
Thinking some more on this, the exhaust testing should be relevant to anyone with a stock 850.
The fuel testing results were virtually the same with my Vincent 998 as with the Commando, so that will apply to a great many engines, basically anything that will run on reg without pinking.
The electrical/charging testing I did would be applicable to anyone using a Podtronics reg/rec.
These were all repeatable values, not seat of the pants.
On performance testing I always make a seat of pants analysis before doing the hill testing. My seat of pants is almost always wrong!
So I think the hill and other testing info should be useful to others.


But you can only lead a horse to water..
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Glen,

Some people will find your testing works for them and benefit from copying it.

Some may find that your tests / ideas don’t work for them, and won’t.

Some may disagree with your hypotheses completely for various reasons.

BUT… your testing and experimenting is definitely of interest to the forum as a whole and ‘adds to the body of knowledge’ as the academics like to say.

Please Carry On.
 
baz said:
It's probably not obvious to many people that some gudgeon pin retaining grooves are machined for wire clips
And some machined for circlips
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And the stamped circlips are installed with the burr(sharp side) oriented outward
 
So in the spirit of thread drift, what factors aside from improper instalation contribute to wrist pin clip failure? Mine was a running bike when I bought it 10 years ago and I never had any issues with it till the clip broke. To be honest I'm not even sure when it happened. Bike always ran OK bit it developed a smoking and backfire issue on the overrun on that side. Motor was (allegedly) built by a well known builder in Philadelphia area. In any event it did not have superblend bearings and had what I was told are "old style" pistons with the slots so I'm thinking that motor was together for a long time.
 
You might try searching Circlip and plug comnoz in as "member"
I was going to post a link but there are several threads with his input on this.
They are all worth a read.

Glen
 
Weren't the slotted pistons prone to blowing the tops off in their days as well, a ticking time bomb really.
 
MikeG said:
So in the spirit of thread drift, what factors aside from improper instalation contribute to wrist pin clip failure? Mine was a running bike when I bought it 10 years ago and I never had any issues with it till the clip broke. To be honest I'm not even sure when it happened. Bike always ran OK bit it developed a smoking and backfire issue on the overrun on that side. Motor was (allegedly) built by a well known builder in Philadelphia area. In any event it did not have superblend bearings and had what I was told are "old style" pistons with the slots so I'm thinking that motor was together for a long time.
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I was a victim of the circlip failure thing... In my case, I was 3 or 4 weeks after a fresh rebuild and the circlip came out at 70mph with a loud "POP" and a puff of blue smoke. The circlips that I had were supplied by a popular norton supplier, so they were being sent out with pistons, but IMO they are not high enough quality. Jim Comstock stated that he thought they might be OK for a lawnmower but would never put them in a motorcycle.

So,... because it happened to me, I've always paid attention to the circlip threads to compare the different scenarios in order to see if there's a common factor that could be identified and maybe corrected...

As it turns out, so far I've seen a variety of circlips fail. The "wire circlips with the big tangs" are just a bad design and pop out on their own. The cut steel ones which seem like a higher quality also have popped out, and some seem to have broken too.

At this point my current build has the cut steel type and they have been in there for years and thousands of miles... Like you, if they were to pop out now, I don't think any smart person would say that they weren't seated correctly after that many miles of use. Sometimes they just popped out after working flawlessly for a long time. It's hard to diagnose something that behaves that way. If I was changing them tomorrow, I wouldn't use either of the circlips mentioned..

I would bite the bullet and buy Jim Schmidt's lightweight pistons. He uses a wire circlip with no tangs on them, so the wrist pin can only push on them at it's outer edge. He also uses a bevel on the end of his wrist pins, so once they are up against the round circlip in it's groove the bevel locks the circlip in that groove... IMO, that's the best design...
 
Generic babble: The lightweight MAP Cycle short skirt pistons for long rids I'm using right now in my Norton have Spiro-Lock clips. Spiro-Lock clips came out if the automotive racing engine world. They must be staying in place. Engine doesn't smoke, snap, crackle, or pop. Definitely not down on power either. BTW, the Spiro-Lock clips are a PITA to install. Jim Schmidt's Wiseco clips were easier to install in the Wiseco pistons that came in the JSM long rod kit.
 
Well I wish I hadn't asked now. I put Emgo pistons with the supplied pins and clips back in. Followed installation instructions about rounded side in so I'm not gonna sweat it. Bike rarely sees 5000 RPM anyway so
 
MikeG said:
Well I wish I hadn't asked now. I put Emgo pistons with the supplied pins and clips back in. Followed installation instructions about rounded side in so I'm not gonna sweat it. Bike rarely sees 5000 RPM anyway so
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They don't always pop out, and that's part of the mystery... It makes any diagnosis of the cause of failure uncertain. When I reported my failure here, more than one person said the problem was installer error. That theme continued until Jim Comstock commented that the circlips in my picture were only good for a lawnmower. (or something to that effect) and were known to fail occasionally. That shut up any of the speculators 🤣

Who knows what the failure rate is on them. As I said, I've also seen the cut style type fail too. In my post about the circlips lots of people pointed out that they had the same circlips as I did and they had no problems so not enough of them fail to be a "known issue", so you're probably fine.

Maybe the angulating back and forth of the connecting rod shouldn't spin the wristpin, but maybe it does in some cases and it imparts some spin to the wrist pin and then maybe that wrist pin spins the circlip and it climbs out of it's groove.... (speculation of course) Whatever the reason, the odds of yours being one that fails is probably less than a 1 percent chance... That's just a guess at the failure rate. I've seen others have circlip failure, but not a lot of others.

At this point I have the cut steel type in a rounded groove for a wire circlip, which is not supposed to work and it has for almost 30 years...
 
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